KVM: selftests: Test x2APIC ICR reserved bits

KVM: selftests: Test x2APIC ICR reserved bits

Actually test x2APIC ICR reserved bits instead of deliberately skipping
them.  The behavior that is observed when IPI virtualization is enabled is
the architecturally correct behavior, KVM is the one who was wrong, i.e.
KVM was missing reserved bit checks.

Fixes: 4b88b1a518b3 ("KVM: selftests: Enhance handling WRMSR ICR register in x2APIC mode")
Link: https://lore.kernel.org/r/20240719235107.3023592-9-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>